Black Hat Search Engine Optimization companies or individuals will try to improve your website's Search Engine Rankings by using certain disapproved
SEO tactics. These tactics can certainly be called a risky business and will probably lead to big disappointments. Through the eyes of a black hat
seo-er a search engine is seen as a competitor.
SEO methods that are used in accordance with search engine guidelines (
see what Google recommends and what they certainly disapprove) are called White Hat
SEO while disapproved methods are called Black Hat
SEO.
You might think that Black Hat techniques are vital for your success in
SEO. Let me tell you one thing: They are NOT! Neither keyword density nor PageRank will ever bring you success; what's more, chasing them can cause huge problems and ruin your
SEO prospects and hopes. Google has been known to remove sites it felt weren't playing fair. Granted, this isn't likely, but why take that risk? Also, much Black Hat
SEO involves some fairly technical work. If this article is your introduction to
SEO, you likely don't have the skills to be a successful Black Hatter anyway -- at least one who doesn't get caught.
So what do you need to avoid if you want to stay on the good side of search engines:
Spam Keyword Stuffing
Keyword stuffing is a deceptive technique to try and elevate a Web site's search engine result ranking by hiding text, so it is unlikely to be seen by a visitor but will be visible to search engines.
This is usually done by making the font color of text match the background color or by making the text very small. Keyword stuffing is ineffective and may get offending Web sites removed from Google's search engine index.
To help prevent having your resource rejected by search engines, just keep to the following recommendations before launching your web site.
1. Look through your text once again. Do you see certain words and phrases dancing in front of your eyes? If not, you can pass your text through to the next test. If you do, try reducing the number of sentences, writing alternative phrases or even consider starting again from scratch.
2. Read out the text of your web page to co-workers or friends or ask them to read it to you. Does it sound annoying or amateurish because of excessive keyword density? If not, the page is ready for launching.
Hidden text
Hidden text is displayed in such a way as to not be easily readable. Hidden text is most commonly achieved by setting the font color to be the same as the background color, rendering the text invisible unless the user highlights it. There is an example of some hidden text on the next line.
To be honoust I think hiding text on your website is big joke. Webmaster that perform such techniques think that hiding "Pamela Anderson" on their beach resort's web page will cause an avalanche of visitors and increase sales. If life was that simple......
Link exchange networks (link farming)
The idea behind link farming is to increase the number of sites that link to yours because search engines such as Google rank sites according to, among other things, the quality and quantity of sites that link to yours. In theory, the more sites that link to yours, the higher your ranking in the search engine results will be because the more links indicate a higher level of popularity among users of the Internet.
However, search engines such as Google consider link farming as a form of spam and have been implementing procedures to banish sites that participate in link farming, so the term link farming has garnered negative connotations across the Internet.
Cloaking
Cloaking is another technology that is widely used by dishonest webmasters. Its effectiveness lies in identifying robots, which crawl around the Web, by their IP addresses or host names. A special doorway page, developed beforehand and polished for SEO purposes but unreadable for humans, is shown to the robot and added to the search engine's index, while a human visitor will see a very different page.
However, modern search engines are able to unmask those who specialise in such tricks. For example, a robot can come from an unknown IP address or disguise itself as numerous human visitors and come from different addresses. Moreover, "sneaking" is encouraged by the managers of some search engines, whereby visitors report that the content of a particular web site found by a search engine has nothing in common with its description on the search engine result page. Then, if a search engine's staff discover that a webmaster is employing illegal methods, his or her site will instantly be ejected from that index.
Doorway pages
A doorway page is a page built specifically for the purpose of ranking well in the search engines and without any real content of its own, and which then links to the "real" destination page, or automatically redirects there. Doorway pages are a popular choice of some SEO firms, although Google has cracked down on this and many webmasters saw their pages disappear from the index. Some SEO firms call their doorway pages something else, in an effort to fool potential customers who know enough to know that they should avoid doorway pages. But a doorway page is still a doorway page even if you call it something else. Some engines may decide that an orphaned page is a doorway page, and if so then the page or the site might suffer a penalty.
Penalties
Its important to know there are 2 different ways of being punished by a search enigine. First of all your website could be
banned. This means that your site hase been removed from the search index completly. Its easy to see if your website is banned from Google. Just do a Google search on
site:yourdomain.com and see if it shows up on the result page. If so, you're not banned.
Secondly your website could be penalized. This means your page rank has reduced. Personally I don't know a way to see if your page rank has dropped down or not. As you know pages change, sites are dropped and so do page ranks -- it's all part of the way the search engines work.
Black Hat SEO - Vital for your success in SEO? 
